1. Field of the Invention
The invention pertains to dielectric films, more particularly the invention pertains to electron beam modification and curing of perhydrosilazane spin-on glass films which are useful for the production of microelectronic devices.
2. Description of the Related Art
The semiconductor industry is rapidly decreasing the dimensions and increasing the density of circuitry and electronic components in integrated circuits. In addition, integrated circuits are being layered or stacked with ever decreasing insulating layer thickness between each circuitry layer.
In the production of advanced integrated circuits that have minimum feature sizes of 0.25 micrometers and below, problems of interconnect RC delay, power consumption and crosstalk become significant. With these decreasing geometries and device sizes, the semiconductor industry has sought to avoid parasitic capacitance and crosstalk noise caused by inadequate insulating layers in the integrated circuits. One way to achieve the desired low RC delay constants involves use of dielectric material in insulating layers that have a low dielectric constant. The use of low dielectric constant (K) materials for interlevel dielectric and intermetal dielectric applications partially mitigate these problems. However, the material candidates which are used by the industry, having dielectric constants significantly lower than the currently employed dense silica, suffer from disadvantages. Most low dielectric constant materials developments use spin-on-glasses and fluorinated plasma chemical vapor deposition SiO2 with K of greater than 3.
Silazane polymers, in particular, perhydrosilazane polymers are known as an insulator material on silicon-based integrated circuits. The formation of perhydrosilazane dielectric layers is known from U.S. Pat. No. 5,922,411. In this reference, a silazane-based polymer is converted into a ceramic material at a reduced temperature by reacting the silazane-based polymer with an amine compound, an acid compound or a peroxide ceramic-transformation promoting agent while in contact with a vapor of steam.
Previous approaches to depositing spin-on glass (SOG) materials such as silazane SOG materials perhydrosilazane polymer films have included a thermal cure of the material after coating to achieve the desired film properties. The draw back to thermal curing is that it requires relatively high temperatures and long curing times. The thermal cure is used to drive out the moisture in the film and provide some level of crosslinking of the material. Some SOG materials can be very sensitive to the process gas, or ambient, used during cure processing. This places additional requirements on the tools and processes used for thermal curing. For some materials the standard thermal cure temperatures (380 to 425xc2x0 C.) and ambient atmospheres, such as nitrogen or argon, are not sufficient to fully cure the material. In these cases catalyst additives are included in the SOG material to help with the curing process. These catalysts add to the complexity of the material and may have an impact on the final film properties of the material. The additives can also increase the cost on manufacturing of the material. The perhydrosilazane polymers used for this invention may optionally contain a catalyst to aid in the curing of the material and make it less sensitive to the ambient used during curing. When a catalyst is not used, very precise control of the cure process is required to achieve the desired film properties.
For the integration of SOG materials into advanced integrated circuit devices there is a drive to reduce the total thermal budget required to process the materials for back-end interconnection. As device geometries are continually reduced, the demand for lower temperature processes increases. For materials that require high temperature thermal process, alternative methods for processing are needed. According to the present invention, an electron beam process is applied to a perhydrosilazane SOG material as a full or partial replacement to the thermal cure process. The electron beam process is more flexible than the thermal cure process in that the time, temperature and ambient atmosphere can be varied in ways that are not possible with the thermal cure process alone. The electron beam process is effective in removing the moisture from the film and a reduction in moisture is seen with increasing electron beam dose. The electron beam process can applied at temperatures substantially below the standard thermal cure process. With an electron beam processing at 200xc2x0 C. and high enough dose, the moisture can be completely removed from the film. By contrast, a standard thermal cure requires a temperature of about 400xc2x0 C. for 60 minutes to achieve the desired film properties. The electron beam process can be carried out in just a few minutes depending on the dose applied. The use of the electron beam process to cure the perhydrosilazane material addresses the issues of lowering the thermal budget of back processing for advanced IC devices. This includes both a reduction in the peak process temperature in addition to the total time at temperature.
The invention provides a process for forming a dielectric coating on a substrate which comprises
a) applying a silazane polymer containing composition onto a substrate,
b) optionally heating the composition to evaporate any solvents therefrom; and
c) overall irradiating the composition with electron beam radiation under conditions sufficient to cure the silazane polymer containing composition.
The invention also provides a process for producing a microelectronic device which comprises
a) applying a silazane polymer containing composition onto an insulating or semiconducting substrate,
b) optionally heating the composition to evaporate any solvents therefrom; and
c) overall irradiating the composition with electron beam radiation under conditions sufficient to cure the silazane polymer containing composition.
The invention further provides a microelectronic device which comprises an insulating or semiconducting substrate and an electron beam cured silazane polymer containing composition on the substrate.
The invention still further provides a process for curing a silazane polymer containing composition which comprises irradiating a silazane polymer containing composition to sufficient electron beam radiation to cure the silazane polymer containing composition.
The invention also provides a process for forming a dielectric coating on a substrate which comprises
a) applying a silazane polymer containing composition onto a substrate,
b) overall irradiating the composition with electron beam radiation under conditions sufficient to cure the silazane polymer containing composition.
The invention further provides a microelectronic device produced by a process which comprises
a) applying a silazane polymer containing composition onto an insulating or semiconducting substrate,
b) optionally heating the composition to evaporate any solvents therefrom; and
c) overall irradiating the composition with electron beam radiation under conditions sufficient to cure the silazane polymer containing composition.